The invention relates to an x-ray diagnostic installation for x-ray tomographic images comprising at least one x-ray tube for the generation of an x-ray beam, a patient support, an image detector and a control generator, connected with the x-ray tube and the image detector, for the purpose of moving the x-ray beam and, synchronously therewith, the image field of the image detector.
In the German OS No. 2,712,320 such an x-ray diagnostic installation is described in which, by means of a synchronous movement of the x-radiation and of the image of the image detector, designed in the form of an x-ray image intensifier, a body layer is imaged in a sharply defined fashion, whereas all other body parts not disposed in this layer are suppressed through blurring. The desired layer can be selected either through alteration of the distance of the image detector from the patient support and the x-ray tube or, in the case of an x-ray image intensifier-television chain, through alteration of the deflection of the electron image in the x-ray image intensifier. The position of the layer is determined through the distances: x-ray tube-body layer and body layer-image detector, so that varying scales of enlargement result which are unknown to the observer. Therefore, mechanical auxiliary means, for example, measuring a tape, a measuring cylinder or a measuring sphere, can be provided in the ray path in order to be able to determine therefrom the dimensions of the body parts. Due to the known geometric dimensions of these auxiliary means, via specific tables, a scale indication can be associated with each layer height. In the case of an x-ray image intensifier-television chain the deflection of the electron image in the x-ray image intensifier determines the layer height so that the dimensions of a body part are to be ascertained here also via tables or mechanical auxiliary means. However, these methods are difficult and time-consuming, so that most frequently they are not employed.